Sealed magnetic snap switch



H. J. ZANDT 3,349,352

SEALED MAGNETIC SNAP SWITCH Original Filed June 12, 1964 INVENTOR.

#42040 zn/var,

BY L

I I fiMw/Mu $514M ATTORNEYS United States PatentO 8 Claims. ((21.335-154 This application is a substitute of application Ser. No.374,610, filed June 12, 1964, now forfeited, and relates to electricalswitching devices. More particularly, it has to do with snap-actingswitches of the type actuated in response to an externally-appliedmagnetic field.

-There.is in current use a form of switch known as a reed switch.Switches of this general type usually consist of a pair of elongated andoverlapping contact members sealed within a non-magnetic non-conductiveenclosure. These contact members are usually made partly or entirely ofa soft magnetic material having contact elements in the gap between themagnetic members which include coatings of noble contact metal. Thecontact members are resiliently-mounted within a sealed nonmagneticenvelope and when subjected to a magnetic field strong enough toovercome the inherent resilience of the members are caused to move bymutual attraction to complete an electrical circuit.

Another configuration of this general type of switch is one having ablade-type contact member resilientlymounted in one end of a sealedcylindrical envelope overlapping relationship to two fixed contactmembers mounted in the opposite end. The suspended end of theresiliently-mounted magnetic contact member is positioned between thetwo fixed members. The fixed contact members, one being of magneticmaterial, and the other being of non-magnetic material, appropriatelycoated with a noble contact material, are arranged so that the suspendedend of the resiliently-mounted contact member is biased against thenon-magnetic member. When this switch configuration is subjected to amagnetic field strong enough to overcome the inherent resilience of theflexible member, the suspended end is attracted away from thenon-magnetic contact member toward the magnetic contact member,interrupting one electrical circuit and completing another circuit. Thistype of reed switch represents a single-pole doublethrow switcharrangement.

Among the advantages of switches whose contact members are actuated bymutual attraction in response to a magnetic field is the fact that theymay be completely sealed in an enclosure to protect the contacts fromthe contaminating effects of dirt, moisture, explosive atmospheres, andother incidents of an industrial atmosphere. In addition, such anarrangement eliminates the necessity for additional mechanical movingmembers in the enclosure.

Although the aforementioned switches are suitable for performing a largevariety of switching operations, their application is limited primarilyby their low current rating due to limited contact fidelity, and becausethereris little force available to open the contacts should over-currentweld the contacts together. The magnetic contacting surfaces must be innearly perfect alignment and mate with each other to obtain eflicientmagnetic actuation conditions. This involves the necessity of veryprecise adjustments of alignment during the manufacture of such devices.The contact elements of these devices generally comprise ferromagneticmaterial, usually iron or iron alloy, plated with high conductivity andcorrosionresistant metal, such as gold, or the like. However, suchcoatings or layers must be very thin, for they also tend to reduce themagnetic eificiency of the switch. Thus,

3,349,352 Patented Oct. 24, 1967 the ferromagnetic portions of themembers must be spaced further apart to allow space for the non-magneticcontact coatings.

Another prior art switch configuration of this type utilizes separatecontact elements, such as buttons, which are attached to theresiliently-mounted overlapping magnetic contact members. These contactelements are generally postioned relatively close to the overlappingportions of the magnetic contacting members to achieve the maximum spacebetween the contact buttons when the switch is de-energized. Therelationship of the contact buttons and magnetic overlap is such as topermit the contact buttons and magnetic overlap elements to engage andyet maintain an absolute minimum space between the members at themagnetic overlap, consequently decreas ing the magnetic efiiciency inaccordance with the square of the distance between the elements. Byminimizing this space at the magnetic overlap to achieve efficientmagnetic performance, the wear allowance of the contact buttons isminimized accordingly, thereby reducing contact life. Although theelectrical continuity through the switch is made primarily through thecontact buttons, the magnetic and electrical circuits are virtuallycoincidental.

Due to insufiicient clearances, continuity must be made over themagnetic gap. This incidental continuity causes surface erosion andwelding at the overlap area, causing premature failure. The electricalcontinuity through the magnetic gap area becomes considerably morefrequent when inductive current loads are interrupted.

The switch configurations aforementioned are further limited torelatively low voltage applications because of the very small electricalclearance between the electrical contact members. These contact members,being in effect solid cantilever beams or blades of soft iron relying ontheir resilience to provide the movement necessary to make contact withtheir mating elements, provide an electrical clearance when de-energizedof only a few thousands of an inch. This relatively small clearance orspace between the overlapping portions of the contact members providesvery limited electrical insulation and tends to cause electricalbreakdown when relatively high voltages are applied to the device.

Furthermore, difiiculties have been encountered with switches of thistype by the accumulation of microscopic particles of iron dust whichform on the contact surfaces or are accumulated thereon during switchuse, Although the contact surfaces are coated with a noble metal or havecontact buttons, these ferromagnetic particles accumulating within thesmall gap tend to form conductive paths between the contact buttons orundesired magnetic flux paths, or both, causing uncontrolled electricalcontin-uity.

A main object of the present invention is to provide a reliablemagnetically-actuated sealed switching apparatus which will alleviatethe aforementioned shortcomings found in the magnetically-actuatedswitching devices of the prior art, and which will also be capable ofconducting and interrupting relatively large load currents with positiveopening and closing operations.

- A further object of the invention is to provide an improved magneticswitch configuration which is suitable for fabrication to producevarious contact arrangements, such as single-pole, normally openswitching devices, single-pole, normally closed switching devices, andsingle-pole double-throw switching devices.

A still further object of the invention is to provide an improvedmagnetically-actuated sealed switching apparatus which lends itselfreadily to modern manufacturing procedures and which inherently providesthe degree of predetermined magnetic as well as electrical values.

A still further object of the invention is to provide an 1 improvedmagnetically-operated switch device which, al-

though capable of controlling larger currents, may be used in preciselythe same combinations as the abovedescribed reed switches of the priorart, namely, may be operated by an externally-applied magnetic fieldprovided by a coil or similar electrically-controlled source of magneticflux, or by a permanent magnet movable into proximity to the switch.

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawing, wherein:

FIGURE 1 is a longitudinal vertical cross-sectional view taken throughone form of magnetically-actuated sealed switching apparatus constructedin accordance with the present invention, namely, of the type havingcontacts which are normally open, the switch being shown in its normalcondition.

FIGURE 2 is a perspective view, in separated positions, of thestationary contact member and the movable contact assembly of the switchillustrated in FIGURE 1.

FIGURE 3 is a perspective view, to a somewhat enlarged scale, showingthe various components of the movable contact assembly of FIGURE 2 inseparated positions.

FIGURE 4 is an enlarged fragmentary perspective view showing the mannerin which the free end of the bowed spring element of the main reedmember seats in the opposing end edge of the adjacent magnetic armatureelement of the movable contact assembly of FIGURES 1 to 3.

FIGURE 5 is a longitudinal vertical cross-sectional view, similar toFIGURE 1, showing another form of sealed magnetic switch assemblyaccording to the present invention wherein the contacts are closed undernormal conditions.

FIGURE 6 is a longitudinal vertical cross-sectional view taken throughstill another form of magneticallyoperated switch according to thepresent invention, this switch being of the single-pole double-throwtype.

Referring to the drawing, and more particularly to FIGURES 1 to 4,inclusive, 11 generally designates a typical embodiment of an improvedmagnetic switch constructed in accordance with the present invention.The switch 11 comprises an elongated, hollow supporting body 12 whichmay be made of glass, but which can also be made from any other suitableimpervious non-magnetic and electrically non-conductive material.Embedded in the opposite ends of the elongated tubular supporting body12 are respective terminal members 13 and 14 which may be made, forexample, from a magnetic nickel-iron alloy, but can be made of any othersuitable material having a coeificient of thermal expansion whichclosely matches that of the glass envelope 12, permitting a glass tometal seal. Terminal member 14 may be solid, but preferably is a tubularelectrode which serves, during the construction of the device, as ameans for evacuating the space between the envelope 12 and filling itwith any desired type of gas at any desired pressure. This gas may besealed within the envelope by permanently closing the tube opening inany suitable manner, as by crimping the member 14, as shown at 15, or bywelding the tube closed. By thus filling the envelope 12 with an inertgas, the operating life of the switch device 11 is greatly extended.

Designated at 16 is a first contact spring arm which is secured to thereduced flattened inner end portion 17 of terminal element 13, as by arivet 18, overlying the fiattened portion 17 and being provided at itsfree end with a depending contact pad or button 19 of suitableconductive material and of proper cross-sectional area from making andbreaking the rated circuit current for which the switch is designed. Asshown in FIGURE 1, the spring arm 16 is mounted so that it can flexupwardly, the upward flexure thereof being limited by an indentation 20formed in the top wall of the envelope 12. The spring arm 16 is made ofrelatively thin resilient metal having suitable electrical conductivity.The contact element 19 may be suitably fastened to the bottom surface ofthe free end portion of the spring arm 16, or alternatively, may be madeintegral with said spring arm.

Designated generally at 21 is a movable contact assembly which issecured to the inner end of the tubular terminal element 14. The movablecontact assembly 21 comprises an elongated flexible leaf spring member22 having attached to its inner end a contact button 23 formed of silveror any other suitable contact material. The inner end portion of thetubular electrode 14 is provided with the reduced flat lug element 24having an arcuately-conc'ave end edge 25 against which isrotatablyengaged the arcuately-curvedconvex end edge '26 of a moving orfloating armature element 27 of magnetic material. Designated at 28 is asupporting arm of non-magnetic material having the upwardly-offset endportion 29 which underlies the right end portion 30 of the leaf springmember 22, as viewed in FIGURES 1 and 3, and is secured therewith to theflattened inner end portion 24 of the tubular terminal member 14.Secured on the end portion of arm 28 opposite member 29 is an armatureelement 32 of magnetic material which is provided with theupwardly-offset end portion 33 which underlies the inner end portion ofthe floating armature member 27, the leaf spring member 22 being formedwith an elongated longitudinally-extending aperture 35 and theoverlapping inner end portions of the armature elements 27 and 32 beingnormally disposed respectively above and below said aperture adjacentthe intermediate portion thereof.

The right end edge of the aperture 35 includes the spring arm 37 whichunderlies and resiliently-supports the floating armature member 27 andbiases said armature upwardly toward a non-magnetic stop arm 38 securedto the inner end lug 24 of terminal member 14.

As shown in FIGURE '3, the stop arm 38 has an apertured end lug 39 whichis fastened to the top surface of the apertured lug 24 of terminalmember 14 and likewise to the end portion 30 of leaf spring member 32and the apertured end portion 29 of arm 28 by a common rivet 40. As willbe readily apparent, the stop arm 38 has an abutment edge 41 which isengaged by the top surface of the floating armature member 27 to limitthe upward movement of said floating armature element. The arm 38 isdownwardly-concave in shape, and its attaching lug 39 is spacedsufliciently from the attaching lug 29 of ,arm 28 by the thickness ofthe supporting lug 24 of terminal member 14 to allow ample clearance forrotation of the floating armature element 27, with the edge 26 pivotedagainst the edge 25, to assure opening and closing of the switch contactelements during the operation of the switch.

Opposite the resilient tongue element '37 the end edge of aperture 35 isformed with ,another resilient tongue element 44 whose end edge ispivotally-engaged in a generally V-shaped groove 45 formed in the innerend edge of the floating armature member 27, as is clearly shown inFIGURE 4. The resilient tongue 44 is normally bowed upwardly and isplaced under tension by its pivotal engagement with the grooved end ofarmature element 27, providing a biasing action which urges the armatureelement '27 upwardly against the edge 41 of a stop arm '38 and whichconsequently exerts a downward biasing force on the inner end portion ofleaf spring 22, biasing the contact button 23 downwardly into engagementwith an indentation 48 formed in the bottom wall of the tubular envelope12. As shown in FIGURE 1, the contact button 23 is thus biased to anopen-circuit position relative to the opposing contact element 19carried by arm 16. When the floating armature member 27 is urgeddownwardly toward the upwardly-ofiset end portion 33 of the bottomgarmature member 32 by a magnetic field, the downward movement of thepivoted edge of finger 44 flexes the leaf spring member 22 past adead-center configuration, causing the free end portion of member 22carrying contact button 23 to snap upwardly and to cause the button 23to rapidly engage the bottom surface of the contact element 19 on arm16. This provides rapid closure of the switch with snap action. When themagnetic field is removed, whereby armature element 27 is free to moveaway from the cooperating magnetic armature portion 33 by the biasingforce of resilient finger 37, the pivoted edge of finger 44 is movedupwardly past the dead-center configuration of the leaf spring member22, causing said leaf spring member to rapidly assume its normalconfiguration, namely, that shown in FIGURE 1, wherein the bottom ofbutton 23 engages the indentation 48.

Armature member 32 is preferably secured to the nonmagnetic arm 28 in apermanent manner, for example, by .a Weld. Similarly, the flat lugmember 24, which is preferably of magnetic material, is secured to theinner end of the tubular terminal member 14 in a permanent manner, forexample, by means of a weld.

The elongated reed member 22 is preferably made of relatively thinnon-magnetic conductive material, such as copper or an alloy thereof,and serves not only as a snapacting leaf spring element to cooperatewith floating armature member 27 to provide toggle action, but alsoserves to provide a current-conducting path from the contact buttonmember 23 to the terminal member 14. The center tongue elements 44 and37 serve as the control means for regulating the movement of thefloating armature element 27. In the normal position of the switch,shown in FIG- URE 1, the finger 37 acts as a resilient support for thearmature element 27, opposing the downward force exerted thereon by thebowed resilient arm 44. The spring arm 37 thus serves as a means tomaintain a small air gap between the overlapping inner end portions ofthe armature members 32 and 27. It will be seen from FIGURES 1 and 2that the spring 37 terminates short of the inner end of the floatingarmature member 27 and also short of the transverse edge 49 of theupwardly-offset stationary armature element 33 so as not to interferewith the air gap between element 33 and the overlying end portion ofarma ture 27 which overlaps it.

It will be noted that the armature 27 automatically aligns itselflongitudinally under the biasing force exerted thereon by thearcuately-curved spring arm 44 because of the arcuate seat 25 providedtherefor on stationary element 24 which receives the convexly-curved endedge 26 of the floating armature element 27. The arcuate seat 25 permitsany necessary self-adjustment of the armature 27 to properly align itsinner end portion with the cooperating stationary armature element 33,providing a substantially articulated joint with respect to itssupporting bearing member 24 and allowing free movement of the floatingarmature element 27 except as restrained by the cooperation therewith ofthe resilient finger elements 44 and 37. As above-mentioned, theresilient finger member 37 provides a cushioned limiting action withrespect to downward movement of the armature element 27 under the springforce exerted thereon by the bowed finger 44,

whereas the resistance of the finger 37 is overcome responsive to theapplication of a magnetic field to the switch, causing the armatureelement 27 to be magnetically attracted toward the stationary armatureelement 33, moving the recessed edge 45 thereof downwardly past thedeadcenter position of the leaf spring member 22, causing said leafspring member to snap in the manner above-described and move button 23suddenly into engagement with contact member 19.

When the device is subjected to an adequate magnetic field, asabove-described, so as to bring the contacts into engagement, theresilient contact arm 16, having substantial resilience, is displacedfrom the top surface of portion 17, as viewed in FIGURE 1, and iselevated until further upward movement thereof is prevented by itsengagement with indentation 20.

During the displacement of arm 16, the accelerated contact button 23 isretarded before converging with the surface of indentation 20, resultingin a cushioning elfect reducing contact bounce. This displacement alsoachieves a desirable sliding action between the contacts.

Consequently, in its return movement, the contact arm 16 acquires acertain momentum before colliding with its normal supporting surface ofportion 17. The impact between these members, in effect, hammers thecontacts apart. This hammering action on contact separation, along withthe sliding action on contact engagement, provides a means of breakingthe bond of welds which incidentally occur and insures increased contactfidelity.

As above-mentioned, the self-aligning feature provided by the arcuateseat 25 which receives the convex arcuate edge 26 of floating armatureelement 27 provides a substantial amount of manufacturing tolerancelatitude while assuring dependable and repetitive performance of theswitch and also increasing the magnetic efiiciency thereof so that aminimum amount of magnetic energy is required to actuate the device.

As above-described, the snap action of the reed member 22 is caused bythe movement of the grooved end 45 of armature 27 past the dead-centerposition of the reed member 22, namely, by the movement of said groovedend past the plane of the reed member. The snap action of the reedmember 22 achieves the desired quick-make and quick-break contact actionto minimize electrical arcing at the contacts. Also, electrical arcingacross the magnetic gap is prevented inasmuch as the magnetic actuatingmechanism is isolated from the electrical contacts of the device.

It will be further noted that by locating the contact button 23 at theend of the reed member 22, its movement is multiplied with respect tothe movement of the grooved end 45 of armature element 27. This factorpermits maintaining a relatively small magnetic gap, whereby to achievea high degree of magnetic efiiciency, while permitting a relativelylarge electrical gap between the contact button 23 and the cooperatingcontact element 19 under open-circuit conditions, without interferingwith the ability of the switch to handle relatively high load currents.

It will be further noted that since the magnetic actuating mechanism isintegral with the contact assembly, adjustment of the magnetic elementsmay be made, with regard to magnetic actuation values and contactperformance, prior to sealing the assembly within the envelope 12.

It will be noted that the support member 28 is provided at its bottomsurface with an abutment lug 50 which bears against the bottom wall ofthe envelope 12, supporting the member 23 and increasing its resistanceto vibration.

Referring now to FIGURE 5, the magnetic switch therein illustrated issimilar to that shown in FIGURES l to 4, except that the switch isarranged as a normally closed switch which opens responsive to theapplication of a magnetic field to the spaced armature elements 27 and32. In the arrangement of FIGURE 5 the spring arm 16 is secured to thebottom surface of the lug 17 with the bottom surface of the inner end ofthe spring arm bearing normally against the indentation 48, and beingurged thereagainst by the contact button 23 which normally engages sameunder the biasing force exerted thereon by the arcuately-bowed finger44. The configuration and arrangement of the movable contact assembly 21is the same as described previously and as illustrated in FIGURES 1 to4, except that the switch is biased normally to a closed position. Whena magnetic field is applied to the switch, whereby to cause floatingarmature member 27 to move toward fixed armature element 33,

the reed member 22 snaps in the manner above-described,

rapidly disengaging contact button 23 from contact element 19.

, FIGURE 6 illustrates a magnetic switch according to this invention inthe form of a double-throw, single-pole switch. The switch, designatedgenerally at 11 has elongated supporting envelope 12' in one end ofwhich is secured the tubular electrode 14 and a movable contact assembly21, similar to that above-described in connection with FIGURES 1 to 5.Embedded in the opposite end of the envelope 12' are respectiveterminals 13 and 13, the terminal 13 being provided with a contact arm16 having a contact element 19 on the bottom surface of its free end, asin the form of the invention illustrated in FIG- URES 1 to 4. Theterminal member 13' is rovided at its inner end with a contactconfiguration similar to that illustrated in FIGURE 5, including aresilient contact arm 16 provided with a contact element 19 on the topsurface of its inner end. The contact element 19 is normally engaged bythe contact button 23 on the inner end of the flexible reed member 22 ofthe movable contact assembly 21. Thus, the terminal member 14 isnormally electricallyconnected to the terminal elements 13', but inresponse to the application of a magnetic field to the switch, as in thecase of the previously-described embodiments of the invention, thefloating armature 27 is urged toward the magnetic stationary armatureelement 33, causing the reed member 22 to snap. This disengages thecontact button 23 from the bottom contact 19' and moves said buttonrapidly into engagement with the upper contact element 19, thusdisconnecting terminal member 14 from terminal member 13 and connectingsaid terminal member 14 to terminal member 13. When the magnetic fieldis removed the parts snap back to their normal positions shown in FIGURE6.

While certain specific embodiments of an improved snap-acting magneticswitch have been disclosed in the foregoing description, it will beundertsood that various modifications within the spirit of the inventionmay occur to those skilled in the art. Therefore, it is intended that nolimitations be placed on the invention except as defined by the scope ofthe appended claims.

What is claimed is:

1. A snap-acting magnetic switch comprising a hollow elongated support,terminal members secured in each end of the support, a first contactelement secured to one of the terminal members inside said support, aflexible. conductive non-magnetic reed member secured to the other saidfirst contact element, said reed member being proterminal member insidesaid support and extending toward vided at its free end with a secondcontact element engageable with said first contact element, a firstmagnetic armature element fixedly-mounted in said support subjacent saidreed member, a second magnetic armature element pivotally-mounted insaid support above said reed member, said armature elements havingoverlapping spaced inner end portions, and a bowed resilientlongitudinal tongue element on the reed member pivotally-engaged withthe inner end portion of said second magnetic armature element andcooperating therewith to exert biasing force on the free end of the reedmember.

2. The switch according to claim 1, wherein said reed member is providedat its free end with a second contact element engageable with said firstcontact element, and wherein said second magnetic armature element ismovable toward said first magnetic armature element responsive to amagnetic field whereby to cause fiexure of said reed member. 7

3. ThesWitch according to claim 2, wherein the inner end of the secondarmature element is provided with a groove pivotally-receiving the endof said tongue element.

4. A snap-acting magnetic switch comprising an elongated support,respective terminal members at opposite ends of the support, a firstcontact element secured to one. of the terminal members, a flexibleconductive reed member secured to the other terminal member and having afree end portion extending adjacent said first contact element, saidfree end portion being provided with a second contact elementconductively-engageable with said first contact element, a fixedmagnetic armature mounted below the intermediate portion of said reedmember, abutment means adjacent said other terminal member, a movablemagnetic armature engaging said abutment means and overlapping saidfixed magnetic armature, toggle spring means extending between the freeend portion of the reed member and the movable magnetic armature andexerting endwise biasing force on the movable armature, and meanslimiting upward movement of said movable armature, said movable armaturebeing movable downwardly towardsaid fixed magnetic armature in responseto a magnetic field to flex the reed member past a dead-centerconfiguration and to thereby produce rapid movement of said secondcontact element relative to said first contact element.

5. The switch according to claim 4 which includes in addition aresilient tongue element on the reed member which extends from the endportion of the reed member, the end edge of the resilient tongue elementbeing pivotally-received in a recess formed in the end of the movablearmature and exerting endwise biasing force on the movable armature.

6. The switch according to claim 5 which includes in addition meanslimiting upward movement of said movable armature.

7. The switch according to claim 4, wherein said abutment means isformed with an arcuate concave seat, and wherein said movable armatureis formed with an arcuate convex end edge which is received in andengages said concave seat.

8. The switch according to claim 4, wherein one of said terminal memberscomprises a metal tube adapted to be employed for filling the hollowsupport with inert gas and to, be subsequently sealed.

References Cited UNITED STATES PATENTS 7/1956 McClain 335-188 4/1959Curzon 335-188

1. A SNAP-ACTING MAGNETIC SWITCH COMPRISING A HOLLOW ELONGATED SUPPORT,TERMINAL MEMBERS SECURED IN EACH END OF THE SUPPORT, A FIRST CONTACTELEMENT SECURED TO ONE OF THE TERMINAL MEMBERS INSIDE SAID SUPPORT, AFLEXIBLE CONDUCTIVE NON-MAGNETIC REED MEMBER SECURED TO THE OTHER SAIDFIRST CONTACT ELEMENT, SAID REED MEMBER BEING PROTERMINAL MEMBER INSIDESAID SUPPORT AND EXTENDING TOWARD VIDED AT ITS FREE END WITH A SECONDCONTACT ELEMENT ENGAGEABLE WITH SAID FIRST CONTACT ELEMENT, A FIRSTMAGNETIC ARMATURE ELEMENT FIXEDLY-MOUNTED IN SAID SUPPORT SUBJACENT SAIDREED MEMBER, A SECOND MAGNETIC ARMATURE ELEMENT PIVOTALLY-MOUNTED INSAID SUPPORT ABOVE SAID REED